With conventional refrigeration systems a regulator for detecting the current refrigeration requirement of a refrigeration location is envisaged in addition to the compressor. If the regulator detects an increased refrigeration requirement, the compressor will be controlled by the regulator in the sense of a capacity increase.
A method for controlling the capacity of a refrigeration system compressor is known from DE 10 2004 048 940 A1, whereby the compressor comprises a pneumatic or hydraulic servo mechanism for an intermittent interruption of the supply of refrigerant to a suction area. The compressor further comprises a regulator, with which a pulse width modulated switching signal can be generated for the pneumatic or hydraulic servo mechanism, for controlling the intermittent interruption of the refrigerant supply. The scan/pause ratio for controlling the pneumatic or hydraulic servo mechanism can be adapted to suit the refrigeration location if necessary.
The valve for influencing the refrigerant flow can also be controlled with a pulse width modulated switching signal as disclosed in EP 982 497 B1, whereby the valve is completely opened in one phase of a time interval, and completely closed in the other phase. The ratio of the two phases reflects the currently required refrigeration requirement of the refrigeration location. By setting the ratio of an opening phase and a closing phase the capacity of the compressor can be set between 0 and 100%. With a cycle time of 10 s it is possible to react very quickly to changes in the refrigeration requirements of the refrigeration location on the one hand, whilst the switching frequency of the valves is limited to a reasonable extent on the other. Although a shorter cycle time would shorten the reaction time to changed conditions at the refrigeration location, the working life of the valves used would also shorten correspondingly.